The earliest known antecedents for curlers of non-circular lids are those employing a press, with the disadvantage of the low production speed and the foreseeable imperfect finish resulting when the container is closed due to the need to allow exit of the lid core.
Later were implemented roller curlers, which generally used two complementary curling rollers with an incomplete finishing that resulted in a complicated closure of the container. These curling defects also cause a sealing compound fillet in a critical position, as the sealing compound wets the corners more than would be desirable.
Regarding sealing compound lining machines, tampon systems are known that use a sealing compound arc with a capacity on the order of 100 lids/min. that cannot provide sealing compound to the lid flange. Equally imperfect is sealing compound showering, also using a non-revolving method, in which a mask leaves open a projection of a multiplicity of small sealing compound droplets that together form a set of aligned points that replaces the sealing compound band, naturally also used for central application of sealing compound and not under the lid curl, although it is three times faster than the immediately preceding system.
Sealing compound lining machines with a discontinuous feed using belts with an indexed (start and stop) motion, with discontinuous lid feeding, have a seriously limited speed even in the only known case where the feed and discharge lines are duplicated as well as duplicating the feed of each one, and struggle to reach 400 lids/min.
In this unique machine a lid is deposited during the stop of the belt and another during its motion, with these lids being sent to corresponding sealing compound lining stations. In these stations and during the stops of the conveyor belt the lid rotates about its axis and the sealing compound, provided with servomechanisms that can only make it rotate about its vertical axis, applies the sealing compound in different angles of inclination resulting in a sealing compound lining band that does not maintain its distance from the lid edge, despite the cost of installing the electronic control servomechanisms for the guns; in addition, the type of lid to which the sealing compound lining is applied cannot be changed as it can only be positioned by gravity, the lids are not discharged with accurate regularity, and the machine cannot operate with any conventional drying oven, nor with two independent ovens or with an oven having two scoop towers.
As regards the lid-feeding device, in the cases described heretofore, with the exception of the aforementioned double feeding system, this is performed with the belt or the rotary base stopped, and under gravity.
One known system involves a lid held in a lower, displaceable base provided with an orifice to allow the lid to fall, together with jack-knife clips that hold the pile of remaining lids placed on top of the lowermost one, until the platform returns and the clips let the lids fall on the un-perforated area of said platform.
Another better-known system is the worm gear, with generally two opposite ones used that feed each lid to a lower platen provided with satellite platens in charge of feeding the lid tangentially and with the lid support stopped.
Finally, regarding discharge devices for curing or sealing compound lining machines, the initial system involved parallel tilt bars that guided the lid and released it after raising it.
This has subsequently been changed by a faster but less efficient system that is effected in an unsynchronised manner, as the lid slides when there is dust on the belt or due to the natural asynchrony from constant use or machine vibrations.
The applicant is not aware of any curling-sealing compound lining machine for non-circular container lids that has the simplicity, speed and is as free of errors and failures in the handling of lids as the one described hereunder.